1. Field of the Invention
The instant invention relates generally to a diffusion transfer image-receptive material. More particularly, it relates to a diffusion transfer image-receptive material in which the surface portion of an alkali impermeable polymer sheet has been provided with alkali permeability.
2. Description of the Prior Art
In general, a diffusion transfer image-receptive material comprises a support and a layer of a hydrophilic high molecular weight material or polymer coated on the support, with the hydrophilic layer containing diffusion transfer nuclei dispersed therein. The above conventional diffusion transfer image-receptive material is usually prepared by dispersing the diffusion transfer nuclei in the hydrophilic high molecular weight material and coating a support with the dispersion. The hydrophilic high molecular weight compounds generally used in the diffusion transfer image-receptive material are, for example, gelatin, polyacrylic acid, a maleic anhydride-methyl methacrylate copolymer, vinyl derivatives such as polyvinyl alcohol and polyvinyl pyrrolidone, cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, metal salts thereof, alginates, and the like.
However, when such conventional transfer image-receptive materials are brought into contact with a silver halide emulsion layer to conduct a diffusion transfer process and thereafter the unnecessary silver halide emulsion layer is removed from the image-receptive material, such materials are accompanied with disadvantages caused by (1) difficulty with the stripability of the silver halide emulsion layer to the extent that a specific strippable layer must be utilized; (2) requiring a considerable period of time to wash with water and dry the image-receptive layer after finishing the diffusion transfer process, or the surface of the image-receptive layer remaining sticky, even after drying. Moreover, there is also the disadvantage that the silver image obtained by the diffusion transfer process is mechanically or chemically weak.
To overcome such disadvantages, an improved image-receptive material containing diffusion transfer nuclei for precipitating silver in a diffusion transfer process throughout the sheet of an alkali impermeable material is known. Such a material is prepared by incorporating the diffusion transfer nuclei in the alkali impermeable material by utilizing vacuum evaporation, and after forming a sheet of the material from a solution of the nuclei-containing material, the sheet is treated chemically to provide an alkali permeability thereto as disclosed in, e.g., Japanese patent publication No. 32754/1969. However, the above image-receptive material has the following disadvantage. That is to say, although a vacuum evaporation apparatus now is quite well-known, it is technically quite difficult to conduct the vacuum evaporation of a material which forms the diffusion transfer nuclei repeatedly under constant conditions, which is necessary in case of manufacturing such specific products on an industrial scale. Also, in the improved technique the diffusion nuclei material is vacuum evaporated on the surface of the alkali impermeable material, the material is then dissolved in a solvent, and after forming a sheet from the solution, the sheet is treated by hydrolysis or the like to provide alkali permeability to a surface portion thereof. Thus, only the surface portion provided with the alkali permeability is effectively utilized in the diffusion transfer process and the diffusion transfer nuclei in the alkali immpermeable portion of the sheet are useless. Furthermore, as a fatal disadvantage, because the sheet of the alkali impermeable material containing the diffusion transfer nuclei is subjected to a treatment such as hydrolysis, the activity of the diffusion transfer nuclei contained therein as silver precipitants on diffusion transfer is reduced.
An object of the instant invention is, therefore, to provide a diffusion transfer image-receptive material not having the disadvantages as mentioned above.
Another object of this invention is to provide a diffusion transfer image-receptive material which can be prepared in a simple manner and has excellent chemical and physical properties.